The correct answer is - B. Mali became primarily a Muslim culture.
Mali and Axum had lot of similarities, but also some differences. While both of them were strong and powerful empires, they had different cultures, and were influenced by different sources.
Mali became influenced heavily by the Islam, thus gradually became a Muslim culture society and empire. Axum on the other hand was not influenced by the Islam, in fact Axum was considered as one of the biggest powers in the world at its peak, and it was the one that interfered in the Arabian Peninsula, not the other way around.